This invention relates to transversely exited (TE) N.sub.2 O lasers and particularly to methods and apparatus for discharge arc suppression in TE N.sub.2 O lasers.
The wavelengths produced by lasers using an N.sub.2 O lasing medium are highly desirable because of their high atmospheric transmission factor. Although the flowing-gas continuous-wave (cw) CO.sub.2 laser can easily be converted to operation on N.sub.2 O wavelengths by the simple replacement of CO.sub.2 by N.sub.2 O in the gas flow, pulsed glow discharge TE laser operation is plagued by discharge arcing when the lasing medium is changed from CO.sub.2 to N.sub.2 O. This is because the disassociative attachment cross sections for N.sub.2 O are one to two orders of magnitude larger than for CO.sub.2 for the range of electron energies expected in the discharge. These large disassociative attachment cross sections of N.sub.2 cause an excessive buildup of negative oxygen ions within the lasing medium which induces discharge arcing.
Conventional methods for controlling discharge arcing generally provide an auxiliary means of ionization which does not depend upon the discharge current. For instance, an injection of a high energy beam of electrons between the discharge electrodes or the ionizing electromagnetic radiation from an auxiliary discharge adjacent to the discharge electrodes, such as a capacitive spark discharge of short duration, may be used. Preionization with an injected electron beam is limited to low ratios of electric field in the discharge to neutral particle density in the discharge so that the discharge is non-sustainable without the electron beam. Neither of these methods is suitable to overcome the high electron attachment rates due to use of the N.sub.2 O medium for lasing, resulting in weak lasing under a limited range of conditions.